Furnace grate bar



Oct. 2, 1951 R. M. L. MARTIN 2,569,639

FURNACE CRATE BAR Filed 001:. 31, 1945 2 Sheets-Sheet 1 I, a H H H ROct. 2, 1951 R. M. L. MARTIN FURNACE CRATE BAR Filed Oct. 51, 1945 2Sheets-Sheet 2 Patented Oct. 2, 1951 FURNACE GRATE BAR Roger MarieLeonce I Application Solid fuels contain water, mineral substancescalled ashes, and a combustible part. Under the action of heat shelteredfrom the air, this latter part disintegrates into two parts, one ofwhich comprises gaseous volatile matters, and the other of whichcomprises coke which generally consists of almost pure carbon.

The volatile matters are set free and will burn when in contact withair. The coke and the ashes remain on the grate. V

In particular the problem of gasifying solid fuels consists first inbringing about the gasification of the carbon contained in the coke andmingled with the ashes, and further in evacuating the ashes in such amanner that no appreciable quantity of carbon is carried along withthem.

Therefore it is necessary to obtain a very even distribution of thegasification air under the whole surface of the fuel bed, as well as thequiet and regular passage of this air through the whole mass of fuel.

This result is very diflicult to obtain because the resistance of themass is irregular in consequence of the difierent sizes of the pieces offuel and the formation of melted ashes which agglomerate into lumps.sistance is formed in part of the fuel bed, the quantity of airincreases in this part of the fuel bed with respect to other partsthereof, and thus the gasification of the fuel and the formation ofchokers accelerates at this part. ensues an intensification of thosephenomena which leads to undesirable results. This is what occurs inparticular with the ordinary grates which consist of bars of triangularsection with the triangle pointing downwards and allowing the air forthe gasificationto pass between them.

In order to overcome this difl'iculty, numerous devices have beenconsidered for the purpose of increasing the resistance presented by thegrate to the passing air.

It is known that for this purpose a grate of thick, closely spacedrectangular bars or a grate consisting of a thick plate provided withcylindrical holes of small diameter may be employed.

increased loss of pressure through the grate When a path of least re-Hence there 7 is obtained by reducing the outlet apertures for Martin,Boulo gne stir-Seine, France October 31, 1945, serial No. 625,841 InFrance June 27, 1945 6 Claims. (01. 110 .30)

2. For the same total flow of air, the section is smaller and the speedof the air therefore is increased, which fact causes dust to be carriedalong with the air and does not produce an equal and regular passage ofthe air through the whole mass of fuel.

-Equal distribution of the air throughout the fuel layer is moredifficult to obtain where the fuel contains ashes and. is in smallpieces. The more ashes there are, the greater will be the risk ofclinkers being formed and of carbon being carried along in the meltedashes. The smaller the pieces of the fuel, the greater is the resistancepresented to the passing air and the greater the risk of lack ofequilibriumbetween the difierent points of-the fuel bed in gasificationor in combustion.

The present invention has for its object to solve these problems and toobtain first a great loss of pressure through the grate, this loss beingeven larger than that through the layer of fuel, and secondly a largesection of passage and a small speed of the air in contact with thefuel, so as to obtain an equal distribution of the air throughout thelayer and a regular combustion.

Grates conforming to the invention are represented by way of example inthe accompanying drawings, in which:

Figure l is a sectional view of a grate showing the inlet conduits forthe air;

Fig. 2 is a plan view of the grate of Fig. 1 as viewed from above;

Figure 3 is a sectional view of another embodiment of a grateconstructed in accordance with the invention and showing the inletconduits for l the air;

Fig. 4 is an elevational view of the grate of Fig. 3 as'viewed from theright hand side thereof Figure 5 is a partial elevational View of agrate formed by several superposed bars;

Figures 6 and 7 show sections through the grate of Fig. 5, respectivelytaken along the lines 6-6 and 'l-| of Figure 5 and looking in thedirection of the arrows; and

Figure 8 represents a vertical sectional view of a gas-producer equippedwith a grate according to the invention.

In the grate shown in Figs. 1 and 2 the conduits for the passage of theair consist of two parts, one 5 in shape of a nozzle on the side wherethe gas enters, and another 6 having the form of an expansion chamber onthe outlet side of the gas. In this way there is produced a strongresistance to the passage of air, a large section of passage for the airwhen contacting the fuel with a small Mi; speed of the air at thisplace.

lee: 1

It is not feasible to place such a grate horizontally, because the smallapertures of the nozzles would be obstructed by the ashes. Therefore itis desirable to place the axes of the nozzles in a substantiallyhorizontal position. In such position the nozzles are not; subject tobeing obstructed by' the ashes.

Such an arrangement is shown in Figs. 3. and 4. where the direction ofair fiow through the nozzles 5 and the expansion chamber 6 issubstantially horizontal.

Figures 5 to '7 show a grate 1 consisting of superposed prismatical bars8 having horizontal supporting surfaces and pierced with horizontalconduits 5" and 6", such arrangement. forming on one side of a nozzle 5"and on the other. side an expansion chamber 6", the bars being providedon the lower side with a notch 9 and on the upper side with a projectingpiece I of same height as the. notch. However, the projecting; piecesand notches are of a little lesser height than that of the horizontalair-expansion chambers through which the air is conducted,

into contact with the fuel.

The grate bars are spaced in Figs. tn 7 mereIy: for descriptivepurposes. Actually they rest. directly on each other.

With a grate thus constituted by superposed bars, a throttling isproduced on the side where the air. enters, and then the conduit sectionis of increased size up to the side of the grate which is in contactwith the fuel, so that the air is at a low speed when it arrives at thefuel.

The bars may be straight, in the form of a crown or of any other shapeaccordingly to whether it is desired to have a level grate, a circulargrate or a grate of a particular form.

The evacuation of the ashes is effected below the grates and may beobtained by means of any known device.

A gas producer equipped with a grate according to the invention isshown, by way of example, in Figure 8.

The apparatus is essentially. constituted. by a grate l according to theinvention, a bottom l2 adapted to support the ashes and clinkersdropping from the grate, a rake 13 to which a reciprocating movement isimparted for extraction of the ashes supported by the bottom l2, anoutlet [4 for the gas located between the two fuel descents, a specialmember I5 separating the feed-hopper from the gas-producer and allowingthe gases to flow towards the. outlet 14, the tubes [6 through whichcirculates air for cool!- ing the member I5, which air thus heated maybe used for the combustion of the produced gas or as air forgasification, a feed-hopper ll containing the fuel supply, and lastlythe shutters l8 separating the hopper from the gas-producer, and placedin the fuel descents IS.

The apparatus to be used maybe of any'other form and may for instance beout along its axis, leaving thus only one slope of descent.

I claim:

1. A flat grate composed of a plurality of parallel arranged grate barshaving each a prismatic shape; a continuous projection on the upper faceof each said prismatic grate bars arranged along and adjacent the outerface of the same; a continuous notch in the bottom surface of each ofsaid grate bars arranged along and adjacent the outer surface ofthe'saine and shaped so that the projection of the adjacent grate barfits into it; a plurality of air passages provided in each 4 of saidgrate bars in the bottom surface thereof and shaped so as to be higherthan said projections on the upper surface of said grate barsimmediately below the passages so that the projection of the adjacentgrate bar reduces the diameter of each of said air passages near theoutersurface of said grate: bar so that each of aid. air pas a e mpose fa relatively row outer portion and a relatively wide inner portion.

2. A flat inclined grate having an outer surface and a fire surface andcomposed of a plu- I rality of superimposed parallel arranged grate rateand. shaped o hat aid.- pr icot onson sa d; rate bars fitinto saidnotches in adjacent rate I bars; a plurality of vertically extendingparallel horizontal air passages provided in each of said grate bars inthe bottom surface thereof and shaped so as to be higher thansaidprojections on the upper surface of said grate bars immediatelybelow the passages so that said projections reduce the cross section ofeach of said air passages near the outer surfaee'of each ofsaid gratebars so that each of said air passages is composed of a relativelynarrow outer portion near said. out r sur a f said f t in l ned state.

and a relativ ly wide inner p rtion near said. fire v surface of saidflat inclined grate.

3,. A fire gra ha n n o ter ur ce and an.

inner surface on which the fuel to be. burned on said grate issupported, said outer surface being substantially parallel to said innersurface, and

said grate having a plurality of substantially parallel rows. eachconsisting of a plurality of spaced sv al a r-pa age formed therein andex: ending from the outer to the. inner surface. of Said ra e. each ofsaid air-passages being com pletely separated and spaced from the otherair v 1 passages and having a cross-sectional areas-uh v stantiallylarger at that portion thereof which is adjacent to said inner surfacethan the cross- 5 sectional area at that portion thereof which isadjacent to said outer surface, each of said airpassages having a lengthfrom said inner surface to said outer surface-which is greater than anytransversal dimension of said air-passages parallel to said surfaces ofsaid grate.

4. A fi e grate h a o ter surfa e and an inner surface on which the fuelto be burned on said grate is supported, said outer surface beingsubstantially parallel to said inner surface, and said grate having aplurality of substantially parallel rows each consisting of a pluralityof pa ed transversal air-passa es formed therein and extending from theouter to the inner S111: face of said grate, each of said airs assagesbeing completely separated and spaced from the other air-passages andhaving a cross-sectional area 4 substantially larger at that portionthereof which is adjacent to Said inner surface than the cross-sectionalarea at that portion thereof whi h is adja ent to said ou surfac h ax sof each of sai a rmassases form n an acute angle with said surfaces, andthe length of each of said air-passages from said inner surface to saidouter surface being greater than any trans versal dimension of saidair-passages parallel to said surfaces of said grate.

5. A fire grate having an outer surface and an inner surface on whichthe fuel to be burned on said grate is supported, said outer surfacebeing substantially parallel to said inner surface, and said gratehaving a plurality of substantially parallel rows each consisting of aplurality of spaced transversal air-passages formed therein andextending from the outer to the inner surfaces of said grate, each ofsaid air-passages being completely separated and spaced from the otherair-passages and having a cross-sectional area substantially larger atthat portion thereof which is adjacent to said inner surface than thecross-sectional area at that portion thereof which is adjacent to saidouter surface, said cross-sectional areas at those portions of each ofsaid air-passages which are adjacent to said inner and outer surfaces,res ectively, being substantially uniform, the axis of each of saidair-passages forming an acute angle with said surfaces, and the lengthof each of said air-passages from said inner surface to said outersurface being greater than any transversal dimension of saidair-passages parallel to said surfaces of said grate.

6. A fire grate having an outer surface and an inner surface on whichthe fuel to be burned on said grate is supported, said outer surfacebeing substantially parallel to said inner surface, and

said grate being composed of a plurality of parallel adjacent barsshaped so as to form between themselves rows consisting of a pluralityof transversal air-passages extending from the outer to the innersurfaces of said grate, each of said air-passages being completelyseparated and spaced from the other air-passages and having across-sectional area substantially larger at that portion thereof whichis adjacent to said inner surface than the cross-sectional area at thatportion thereof which is adjacent to said outer surface, saidcross-sectional areas at those portions of each of said air-passageswhich are adjacent to said inner and outer surfaces, respectively, beingsubstantially uniform, the axis of each of said air-passages forming anacute angle with said surfaces, and the length of each of saidairpassages from said inner surface to said outer surface being greaterthan any transversal dimension of said air-passages parallel to saidsurfaces of said grate.

ROGER MARIE LEONCE MARTIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 581,347 Greene Apr. 27, 1897689,827 McClave Dec. 24, 1901 702,538 Campbell June 17, 1902 1,026,645Bigelow May 14, 1912 1,464,190 Webster Aug. 7, 1923 1,553,587 BalmfirthSept. 15, 1925 1,769,157 Newkirk July 1, 1930 1,843,000 Rich Jan. 26,1932 1,895,511 Hulson Jan. 21, 1933 1,989,514 Harlow Jan. 29, 19352,070,894 Gorsuch Feb. 16, 1937 FOREIGN PATENTS Number Country Date18,326 Great Britain Nov. 1, 1890 548,213 France Jan. 10, 1923

